An occupant protection device for helping to protect an occupant of a seat of a vehicle may include a vehicle sensitive sensor assembly. The vehicle sensitive sensor assembly activates the occupant protection device to help protect the occupant of the seat. The vehicle sensitive sensor assembly is responsive to certain vehicle conditions, such as vehicle deceleration and tilt. The vehicle sensitive sensor may prevent rotation of the spool of a retractor in a belt withdrawal direction in response to sensed vehicle conditions.
The vehicle sensitive sensor assembly may include an inertia member movable relative to a support to prevent rotation of the spool in the belt withdrawal direction. The support may have a spherical cavity. The sensor may cause unwanted or nuisance locking of the spool in response to vehicle conditions, such as vehicle vibration.